The ability to reduce the surface tension of water is of great importance in waterborne coatings, inks, adhesives, and agricultural formulations because decreased surface tension translates to enhanced substrate wetting in actual formulations. Surface tension reduction in water-based systems is generally achieved through the addition of surfactants. Performance attributes resulting from the addition of surfactants include enhanced surface coverage, fewer defects, and more uniform distribution. Equilibrium surface tension performance is important when the system is at rest. However, the ability to reduce surface tension under dynamic conditions is of great importance in applications where high surface creation rates are utilized. Such applications include spraying, rolling and brushing of coatings or spraying of agricultural formulations, or high speed gravure or ink-jet printing. Dynamic surface tension is a fundamental quantity which provides a measure of the ability of a surfactant to reduce surface tension and provide wetting under such high speed application conditions.
Traditional nonionic surfactants such as alkylphenol or alcohol ethoxylates, and ethylene oxide (EO)/propylene oxide (PO) copolymers have excellent equilibrium surface tension performance but are generally characterized as having poor dynamic surface tension reduction. In contrast, certain anionic surfactants such as sodium dialkyl sulfosuccinates can provide good dynamic results, but these are very foamy and impart water sensitivity to the finished coating. The problem of foaming is particularly troublesome in aqueous photoresist developers used in semiconductor fabrication.
The demands of semiconductor manufacture have required the use of high performance surfactants and wetting agents in photoresist developer formulations. As line features shrink to smaller sizes and photoresist substrate materials become more aliphatic in nature (i.e. having lower surface energy), aqueous developer solutions are being formulated with surface tension reducing agents. Another requirement for these developers is that they have a low tendency to foam. This is accentuated by the movement toward larger wafer sizes. Low foam formation is particularly important when using spray-puddle techniques because microbubble entrainment during spreading of the solution over the photoresist surface can lead to defects. Surfactants that have been used in the past to increase wetting of the photoresist typically lead to higher foam formation. For the most part the industry has focused on the effect of surfactant on photoresist performance, such as contrast, critical dimension, and feature sharpness. Although the cleaning ability of underlying substrates is enhanced by typical surfactants, foam formation still remains a problem.
There is a need for a family of surfactants which provide good equilibrium and dynamic surface tension properties, are low-foaming, are liquids at room temperature to facilitate handling, are stable under basic conditions and would be widely accepted in waterborne coating, ink, adhesive, fountain solution, agricultural and electronics cleaning formulations.
The importance of reducing equilibrium and dynamic surface tension in applications such as coatings, inks, adhesives, fountain solutions, agricultural formulations and electronics cleaning compositions, e.g., aqueous developer solutions for making semiconductor devices, is well-appreciated in the art.
Low dynamic surface tension is of great importance in the application of waterborne coatings. In an article, Schwartz, J. "The Importance of Low Dynamic Surface Tension in Waterborne Coatings", Journal of Coatings Technology, September 1992, there is a discussion of surface tension properties in waterborne coatings and a discussion of dynamic surface tension in such coatings. Equilibrium and dynamic surface tension were evaluated for several surface active agents. It is pointed out that low dynamic surface tension is an important factor in achieving superior film formation in waterborne coatings. Dynamic coating application methods require surfactants with low dynamic surface tensions in order to prevent defects such as retraction, craters, and foam.
Efficient application of agricultural products is also highly dependent on the dynamic surface tension properties of the formulation. In an article, Wirth, W.; Storp, S.; Jacobsen, W. "Mechanisms Controlling Leaf Retention of Agricultural Spray Solutions"; Pestic. Sci. 1991, 33, 411-420, the relationship between the dynamic surface tension of agricultural formulations and the ability of these formulations to be retained on a leaf was studied. These workers observed a good correlation between retention values and dynamic surface tension, with more effective retention of formulations exhibiting low dynamic surface tension.
Low dynamic surface tension is also important in high-speed printing as discussed in the article "Using Surfactants to Formulate VOC Compliant Waterbased Inks", Medina, S. W.; Sutovich, M. N. Am. Ink Maker 1994, 72 (2), 32-38. In this article, it is stated that equilibrium surface tensions (ESTs) are pertinent only to ink systems at rest. EST values, however, are not good indicators of performance in the dynamic, high speed printing environment under which the ink is used. Dynamic surface tension is a more appropriate property. This dynamic measurement is an indicator of the ability of the surfactant to migrate to a newly created ink/substrate interface to provide wetting during high speed printing.
Tetramethylammonium hydroxide (TMAH) is the chemical of choice in aqueous alkaline solutions for developing photoresists according to Microlithography, Science and Technology, edited by J. R. Sheats and B. W. Smith, Marcel Dekker, Inc., 1998, pp 551-553. Surfactants are added to the aqueous TMAH solutions to reduce development time and scumming and to improve surface wetting.
U.S. Pat. No. 5,098,478 discloses water-based ink compositions comprising water, a pigment, a nonionic surfactant and a solubilizing agent for the nonionic surfactant. Dynamic surface tension in ink compositions for publication gravure printing must be reduced to a level of about 25 to 40 dynes/cm to assure that printability problems will not be encountered.
U.S. Pat. No. 5,562,762 discloses an aqueous jet ink of water, dissolved dyes and a tertiary amine having two polyethoxylate substituents and that low dynamic surface tension is important in ink jet printing.
Although many monoalkylated aminoalkylpiperazine derivatives have been reported, it has not been recognized these materials possess surface active properties.
U.S. Pat. No. 3,007,929 discloses compounds of the form ##STR2## where R is a C8 to C16 linear alkyl group. Aqueous solutions of the C12 and C14 derivatives were effective sterilizing and disinfecting agents for food containers and kitchen utensils.
Zagudullin and Baimetov [J. Gen. Chem. USSR (Engl. Transl.) 1991, 61, 889-894; Zh. Obshch. Khim. 1991, 61, 978-985] report the alkylation of aminoethylpiperazine with ethyl chloride, allyl and methallyl chlorides, and chloropropenes. Depending on reaction conditions and the amount of alkylating agent used, mono-, di-, or tri-allyl and -methallyl derivatives can be formed: ##STR3## where R.dbd.H or CH.sub.3. The workers also report the formation of compounds of the form ##STR4## Alkylated aminoethylpiperazine compounds are said in this article to be important as catalysts in the synthesis of polyurethanes, polyamines, and epoxy resins. They are also said to be useful as selective solvents and as auxiliary agents in the textile industry.
JP 01 38,080 discloses a class of compounds of the structure ##STR5## where R.sup.1 can be C3-C8 linear or branched aliphatic,
R.sup.2 and R.sup.3 can be C3-C11 linear or branched aliphatic, PA1 one of R.sup.2 or R.sup.3 must be H or C1-C2, PA1 R.sup.4 is H or C1-C12 linear or branched alkyl, PA1 m and n are each an integer from 0 to 3 with m+n.ltoreq.3, PA1 p is an integer from 2-13. PA1 an ability to formulate water-borne coatings, inks, fountain solutions and agricultural compositions which may be applied to a variety of substrates with excellent wetting of substrate surfaces including contaminated and low energy surfaces; PA1 an ability to provide a reduction in coating or printing defects such as orange peel and flow/leveling deficiencies; PA1 an ability to produce water-borne coatings and inks which have low volatile organic content, thus making these surfactants environmentally favorable; PA1 an ability to formulate coating and ink compositions capable of high speed application; and PA1 an ability to formulate compositions which retain excellent dynamic surface tension properties under strongly basic, high temperature environments. PA1 an ability to formulate low surface tension aqueous electronics cleaning and processing solutions, including photoresist developer solutions, for the semiconductor manufacturing industry with good wetting and extremely low foam.
Specifically shown is 1-[3-[4-methyl-1-(3-methylbutyl)pentylamino]propyl]piperazine. These compounds are disclosed as central nervous system agents and insecticides.
There are few references describing low foam surfactants in developer compositions. JP 10-319606 discloses that commercially available ethylene oxide (EO)/propylene oxide (PO) block polymers give good wetting and low foam.
JP 03-062034 discloses polyoxyalkylene dimethyl polysiloxanes as good surfactants with low foam in developer formulations. Polysiloxanes are known to rearrange or decompose under conditions of high pH.
Although there are a few references to the use of amines in photoresist developer compositions, they are not related to the use of surface active agents. U.S. Pat. No. 5,252,436 discloses the use of relatively high levels of amine additives (3-30 wt %) and U.S. Pat. No. 5,039,595 uses amine additives at levels of 5-50 wt %. Both of these disclosures appear to be using the amines to alter the bulk solvent properties of the developer solution.
U.S. Pat. No. 4,997,748 discloses cyclic nitrogen compounds at levels of 0.1 to 10 wt % to decrease scum formation and enhance image sharpness during photoresist development. Among the cyclic nitrogen compounds taught is the cyclic urea 1,3-dimethyl-2-imidazolidinone. Since the nitrogen compounds are not amphipathic, it is not likely that they will lower surface tensions at low concentrations, and their utility appears to be based on properties other than surface tension reduction. 1,3-dimethyl-2-imidazolidinone is well known as a very good solvent and not as a surface-active material.
U.S. Pat. No. 4,828,965 discloses the use of lower alkanolamines (1-4 carbons) in combination with alcohols at concentrations of 0.40-5 wt %.
U.S. Pat. No. 4,741,989 discloses the use of small amounts of amines to modify the reaction chemistry of the quinonediazide photoactive compounds in photoresists, but only small chain amines are used and no surface active amines are cited.
U.S. Pat. No. 4,628,023 discloses water soluble amines as the alkali source for developer solutions. Because the preferred pH range is above 12.5, the use of organic amines would necessarily be at high concentrations.
JP 61-179651 discloses the use of amine-containing developer solutions with surface tensions of between 25 and 50 dyne/cm. These surface tensions are achieved by the use of relatively large amounts of non-surface-active amines (3-5 wt %) in combination with tetramethylammonium hydroxide as the base.